Monitoring of temperature distribution in a thin film heater by an array of a-Si:H temperature sensors

In this paper, we propose the use of an array of amorphous silicon (a-Si:H) p-i-n diodes to monitor the spatial temperature distribution over a thin film heater used for thermal treatments in lab-on-chip systems. The effects of heater geometry and operating conditions on the spatial temperature distribution have been preliminarily investigated by using COMSOL Multiphysics, coupling the electrostatic problem with the thermal problem via the Joule effect. Depending on the analyzed system, nonuniform temperature profiles can be induced over the heater surface revealing the need for a temperature point-monitoring. An example of whole device, constituted by a serpentine shaped TiW/Al/TiW thin film heater and five a-Si:H diodes deposited between the resistor meanders, has been fabricated on a microscope glass slide and characterized. Voltage-temperature characteristics of the a-Si:H sensors, measured at constant forward current, show a sensitivity around 2.8mV/°C. The spatial temperature distribution along the heater has been derived measuring the voltage across each a-Si:H diode. A good agreement between modeled and measured data is obtained, demonstrating the suitability of the a-Si:H array as temperature distribution sensors in lab-on-chip application. © 2011 IEEE.